add php 7.3 to testing

Author: michaeldyrynda

.travis.yml

@@ -32,6 +32,16 @@ matrix:
       env: ILLUMINATE_VERSION=5.7.*
     - php: 7.2
       env: ILLUMINATE_VERSION=5.8.*
+    - php: 7.3
+      env: ILLUMINATE_VERSION=5.4.*
+    - php: 7.3
+      env: ILLUMINATE_VERSION=5.5.*
+    - php: 7.3
+      env: ILLUMINATE_VERSION=5.6.*
+    - php: 7.3
+      env: ILLUMINATE_VERSION=5.7.*
+    - php: 7.3
+      env: ILLUMINATE_VERSION=5.8.*
 
 before_install: travis_retry composer require "illuminate/database:${ILLUMINATE_VERSION}" "illuminate/events:${ILLUMINATE_VERSION}" --no-update -v